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Computer pioneer and Second World War codebreaker Alan Turing is to feature on the new £50 note, the Bank of England has confirmed.

The announcement was made at the Science and Industry Museum in Manchester on Monday (July 15).

Mr Turing is known for his links to Bletchley and Wilmslow, but from his mid-teens in the late 1920s he was based at the family home in Ennismore Avenue, near Stoke Park in Guildford. After leaving for Cambridge University he would often visit the town to stay with his mother or his brother’s family until his death in 1954.

Paul Backhouse, author of Alan Turing: Guildford’s best kept secret, spoke to SurreyLive on the release of the book in 2016. He dubbed the mathematician the "son of Guildford".

“About 10 years ago I went to Bletchley Park for just a day and became curious about Alan Turing,” Mr Backhouse said at the time.

“I bought a biography and was thumbing through and found he lived in Guildford. I thought ‘oh my god’. I didn’t know he lived in Guildford, about five minutes from where I live.”

Mark Carney, governor of the Bank of England, said: "Alan Turing was an outstanding mathematician whose work has had an enormous impact on how we live today." (Image: Christopher Furlong/Getty Images)

He began his research, initially to plan guided "Turing walks", but came up against challenges that were very particular to his subject.

The codebreaking work, which was instrumental in winning the Second World War, was classified until nearly two decades after Turing’s untimely death.

His work in computing helped shape the digital age but its importance was not appreciated at the time, even by many fellow mathematicians. The significance of the "Turing Test" may only be understood in the coming decades, as progress is made in the field of artificial intelligence.

The only reference in the Surrey Advertiser to Turing, during his lifetime, was a report from 1934 of his brother John’s wedding, at which he was best man.

A cutting from the Surrey Advertiser and County Times from September 1, 1934, reporting on the wedding of John Turing, at which Alan was best man

“All the appeals [for information] I’ve done I’ve drawn a blank because when he was visiting Guildford he wasn’t famous,” said Mr Backhouse.

“When Lewis Carroll came to Guildford he was already well known. Alan Turing came [visited] in the 1950s and no one had a clue what he did in the war, and what he did to pave the way for the digital revolution.”

Mr Backhouse turned to sources including Alan Turing’s niece and nephew, as well as the biography by Alan Turing’s mother, Sara, published in 1959, before anything was known of his wartime achievements.

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Sara’s book revealed that Guildford may in fact have played an active role in her son’s success.

“In the vacations, Alan and I had long walks together and whole days out when he would talk about his work and plans to research into the foundations of mathematics,” she wrote.

“Certain places around Guildford are associated with ‘variable’ and ‘constants’ and the square root of -1.”

Alan’s nephew, Dermot, told an audience at Guildford Book Festival in 2015 that the mathematician did not much like the town, but Mr Backhouse said that it was more the family situation that was the problem.

“His parents started to drift apart and eventually separated, and his father died shortly afterwards,” said Mr Backhouse.

“After John left home, when Alan was in his late teens and at university he was coming back to his parents squabbling, and I think he was probably bored really and looking to get away to see friends.”

Guildford was certainly more parochial at the time, and probably not the ideal place in which to be a gay mathematical genius, but Mr Backhouse said: “He came back to see his mother and John and his (Dermot’s) half-sisters.

“I haven’t found anything where he said that Guildford was an awful place.”

Alan Turing’s life ended in tragedy.

Homosexuality was still illegal in the 1950s and he was convicted of indecency in 1952. Whatever his family suspected his sexuality was certainly not public.

Alan Turing - the 'son of Guildford'

Mr Backhouse said: “After his arrest he told his brother he was gay and said: ‘Can you tell her [their mother] what happened?’

“So he came down to South Hill [his mother moved there after the marriage failed] to tell her.”

Turing accepted a sentence of hormone therapy, or "chemical castration", and two years later he was found dead at the age of 41 from cyanide poisoning in his flat in Wilmslow, near Manchester.

On June 8 1954, police called John Turing to break the news, but John was at the cinema – most likely the Odeon, at the junction of Epsom Road and London Road, which was showing Henri-Georges Clouzot’s The Wages of Fear.

“John later recalled that he got home with one of his daughters at about 10.30pm to find the message from the Manchester police about Alan’s death,” said Mr Backhouse.

“He went up to Manchester next day to formally identify Alan’s body.”

Alan Turing lived near Bletchley throughout the war, and for a while was in Teddington before spending his final years in Wilmslow, but Mr Backhouse said that "Guildford you can trace from 15 to his death".

“I think what this research has done,” he said, “is shown that we can claim that Alan Turing was a ‘son of Guildford’.”

There is a statue of Alan Turing at the University of Surrey (Image: Steve Porter/Surrey Advertiser)

While Mr Turing is perhaps best-known for his work devising code-breaking machines during the Second World War, which was portrayed in a film starring Benedict Cumberbatch, he played a pivotal role in the development of early computers, first at the National Physical Laboratory and later at the University of Manchester.

He laid the foundations for work on artificial intelligence by considering the question of whether machines could think.

The new polymer £50 note is expected to enter circulation by the end of 2021.

It will feature a quote from Turing, given in an interview to the Times newspaper on June 11 1949: "This is only a foretaste of what is to come, and only the shadow of what is going to be."

Alan Turing: Guildford’s best kept secret, is available to buy online and in all good bookshops.